Method of fastening two part plastic fastener by fusion from frictional heat of rotation



June 28, 1960 J, W. ANDERSON METHOD OF FASTENING TWO PART PLASTICFASTENER BY FUSION FROM FRICTIONAL HEAT OF ROTATION Filed 001;. 18, 1954ressure bond by heat of 7 /7 INVENTOR United States Patent John WileyAnderson, Newtown, Conn. Plastic Molding Corp., Sandy Hook, Conn.) V

7 Filed Oct.p18, 1954, Ser. No. 462,966

' Claims. Cl. 218-29) invention relates to a two-part, pos t type offastener in which each part comprises a headed body of thermoplasticresin. The invention further relates to a method of bonding such headedfastener parts together by coalescence of the thcrmoplastic at mutuallycontacting surfaces of the fastener parts.

An object of the invention is to produce such coalescence by' theapplication of relative rotary movement to portions of the fastenerparts that taper, while such parts are in surface contact under axialpressure, thereby to avoid the use of screw threads, heading overoperations, eyelet setting operations and the like 'for securing thefastener parts together.

A related object is to reenforce the binding strength of such a fastenerby causing mechanical deformation of telescopically intrengaged portionsinto interlocking engagement, and to preyent at least one of thefastener parts from turning relative to the work material to be bound2,942,748 Patented June 28, 1960 drical external surface and is madehollow by an elon gate socket 15 central thereof which opens through.the end of shank 14 remote from head 12.- Socket 15 tapers in relationto the axis at an angle of approximately one or two degrees, its largerendbeing at the mouth 17 where the taper is relation to the axis mayincrease to, say, Seven'degrees approximately. Here the socket 15 iscountersunk steeply at a somewhat more flaring angle of taper. This soweakens .the tubular shank wall 14- at. the mouth of the socket that itcan be flared outward from its full line shape to its broken line shapein Fig. 2. This strengthens the holding engagement of the sleevemember-glfi'with a work piece W through which the sleeve member 10extends. Sleeve member 10 may also extend; through an associated workpiece W that is to be secured to work piece W in face to face contacttherewith by the: fastener. 'A multiplicity 'of such work pieces can besandwiched between outer plies, as laminae, thereby to be held togetherby-my improved fastener. The material; of the work pieces may be hard orsoft and their surfaces rough or smooth.

The head 12 may be slotted asinFigs. 3 and 4 tore ceive a screw driver,or may be recessed as in Fig. 1 to receive a plug wrench, or may be flatsided as in Figs. 5, 6 and 8 to be engaged by a conventional jaw wrenchor socket wrenchor by a machine chuck. While in the drawings thesevarious styles of head are illustrated in partiallybroken away,constructed and applied to work in accordance with the presentinvention.

Fig. 2 shows partly in section on the plane 2-2 in Fig. 3 a modifiedform of fastener whose overlapping shank portions are in process ofbeing assembled.

Fig. 3 is a plan view of the fastener of Fig. 2.

Fig. 4 shows portions of the fastener shanks of Fig. 2 in fullyassembled relation.

Fig. 5' shows a further modified construction of the two-part fastenerin process of being assembled.

Fig. 6 is a plan view of the fastener of Fig. 5.

Figs. 7 and 8 show different portions of the fastener shanks of Fig. 5in fully assembled relation.

The drawings illustrate optional forms of heads and engaged shanks oneach of cooperative members that are to be united by practicing themethod of this invention to form a fastener embodying the invention.Each of the members comprises a body of synthetic molded thermoplasticresin having physical properties suitable for the purposes of theinvention such as nylon. Properties that are desirable in thethermoplastic material of the two members include an ability to react toan application of heat so that their surfaces will fuse together intomutually bonded relationship. Specifically it has been discovered thatsufficient heat can be produced by the friction generated by merelyrubbing together conical contacting surfaces of two such fastenermembers.

Referring to Figs. 1 and 2, one of the thermoplastic bodies comprises asleeve member 10 molded to a shape that somewhat resembles a hollowrivet, comprising a head 12 or 12' and a shank 14. The latter has acylinconnection with plu'g member 11 which is next to'be described, ahead of any of these styles can as readily be providedlon the sleevemember '10 of the fastener. The other ,or plug member '11, 11a.,or 11boflthe fastener comprises a head 13 and a shank 16: which tapers at thesame angle as does socket 15 formost of its length. .Inashort portion ofits length adjacent the head .13, 'shank'16 has a steeper, taper at. 18that accords withithetaper of the socket mouth at 17 in sleeve member 10 The opposite smaller e nd of shank-.16, contains a conicalrecess 21that accords in shape iwth a conical 22 'formed at/the bottom ofsocketjlS. l i

in practicing the invention layers of workfsuch as W and W that are tobe fastened together are provided with aligned. holes of equal sizereceptive to and fittingsthe hollow shank 14 of sleeve member 10. Thecombined thickness of the work should be at least as greatjas the lengthof shank "14 but not greater unless thework mate rial issufiicientlysOftor yielding to be compressible.

. In use'of the fastener as a hinge or pivot pin the comhine'dthicknessof multiple work pieces swiugably coupled together thereby should besufiiciently less than the length ofshank 14 to provide clearancefor-permitting freedoni of swinging movement of the workpieces relativeto'one another and to the fastener.

The head 12 of sleeve member 10 will be supported firmly against thrustin an axial direction and held from rotating by any suitable means suchas wrench, chuck or vice while the shank 16 of plug member 11 isinsorted in socket 15. If its shank is about 7 in diameter the plugmember will be rotated in socket 15 at a speed of about two thousand tothree thousand r.p.m., more or less, by rotary power drive of its head13. While thus being rotated plug member 11 is subjected to a thrust often to fifteen pounds in an axial direction against the tubular walls ofthe socket 15 While shank 16 is telescopically nested in the latter.Such thrust is applied by any suitable power tool such as in a drillpress as a drill by hand feeding is forced endwise against the work thatis to be drilled. This sets up friction between the similarly tapering,mutually contacting surfaces of shank 16 and sleeve member 14 such thatsuiflcient heat is generated to fuse said mutually contacting surfacesof the thermoplastic material of the fastener parts into a bonded u'nionwithinfive to ten seconds;v bond becomes permanent'and strong afterrotation has' ftoa point of fusibm whereby said "contacting surfaces of[a said members are caused to coalesce.

ceased and the fu sed together surfacesof the fastener 'm'embe'rs havecooled"wbile[ remaining pressed together- -'I-.he tendency of the moresteeplyiapered shank portiion#18 of 'plug memberilfl -toexpandtheyieldablehOllo'w- 'fsleev e' shank diamtrieallyat socket mouth 17 causesthe V tubular wallsll t at this end of sleeve member 10 to press 7radially 'oiitvi/ard against the material of work pie'cej-W whereby towedge-member 10 "in the work. helps in"opposingrelativerotaryxdisplacement of the-sleeve mienibeirelative' to the work.7 V 1 In fFi'gs. 5.-and 7 an additional clinging together strength ofthe fastener members results from "forcing; annu- *lar eagesgz tdfshank16', which are wedge-' sh-apedin iadialpr ofileQinto outward flaringengagement with 'an v outwardly fiar'ed 'annularjgroove 23 of,dovetaiksh'ape 7 thatiis laterally-undercut infthe head 12 about the'base 7 6f the" slope "of-the conical-boss 2z at 'the bo ttom or V blindnd'of socket-l5 asshown in-Fig. 7Q This'inter loekling e'ngagement ofshankend 24 rwiththre undercut h rmnular 'groove 23 takesrplace just' berforethe cavitated end'21 of'shank 16 bottoms on the conical boss zzrandcan result from the 'aforesaid axial thrust :on the parts w en their-surfacesgare sufliciently warmed and softened ye spinnin'gpof-theparts? e The appended claims are -directedto :and intended to bver all'variations of the exact shapegsizes and mateby the heat of frictionwhether or not =-accompanied by iel' 2. The method of fastening togetherplural plies of work sheets comprising thetsteps of, projecting throughsheets of work material a headed hollow sleeve member of thermoplasticresin having an internal curved surface 7 0t' ape '-m 9 t, ins ingaicorresp ndi yaapered c umed; surface of the shank portion fof a headedplug member of thermoplastic resin inside ofsaidhsleeye m'emher in atleast Partially telescope' d relation thereto, pressing said taperingsurfaces ;of 'said pmemliersfltogether in' force with which tthe saidtapering membersgarepress'ed rial 6f fas'tener' parts hereini mentioned;well as "all 'i i'riiriatioris-of the exactpre ssuresandgspedsfofrotation I suggested or-sucessfulipractic'eoftheinventionascom'e v t 'w din v f the taperingicbnformityfto thecontour ofjatleast part, of

' the "shankjportion "of'fthe' other of said members, telescopingsaidshank portions, and pressing the shank portiorr' 'of' ne of said membersaxiallyjagainst the shank 'viith "the shank portion of t e a other ofsaid --memb ers,

the fierce of said pressure: and the speed iQfj isaid rotary the" otherof said members iwhileisimultanemovement being suflicient to heat saidthermoplastic mat'ei'ialY'at the contacting surfaces of said; shankportions together is approximately between ten and fifteen thQ rdefid-in=.:cl im; 2,-in'-whih"the. :said

speed of rotations-is betweenrtwoithousand gandrthree thousandrevolutions per: minute-and the --said: tapering 'members @repressedtogetherywith agforce ofrzapproagimately :between ten andfifteenipoundsrduringtheirrrela- V .Q-Refereneescitedzmvthefilepfthisipatent p I "OTHER REFERENCES V I j ModernPlastics, -Noyember 1945, pagesn1421'45, article Fabricating withFrictional Heat. by zRobertN. Fr'eres, copy 1. available. in class 1 8,Resh'ape' 1 Digest and in the Patent :OfiiceScien'tific Library. 7 1

v V 'U IT EST PAilf NTS a 5 r r p 7 :1 1i238,'010fljfThomas 'f" m h difii i't fi i bti i t l ii d" a H to jformia fastenerj the, shank:portions 'respec- V i trvely tif a headed plug -memberiand ofiafheadeds'leeve' o mbe'rj-both comprising abody offusiblejthermoplastic I ersin,which includes the isteps of, contou'ringjat least i r of theshank'portion'fof one .of said members in 4 mail-L

